According to Aristotle, a tragedy must

According to Aristotle, a tragedy must always respect three aspects, or, three unities. The unity of time, the unity of place, and the unity of action. This means that a tragedy must always be watched in one sitting, up to a maximum of 24 hours of length; it must be held in its entirety at a single place; and one should not have multiple parallel plots and should focus on just one action.